The present invention relates to a feed mechanism of a sewing machine.
The feed mechanism of a sewing machine of a swingable lever type has been simplified in structure, but has not been satisfactory for a fabric feed function of a feed dog.
For example, in a device shown in FIG. 6, a horizontal feed shaft 1 is pivoted, via a pin 4, at a feed bed 3 which has a feed dog 2, and the feed dog 2 is moved vertically via a feed adjusting plate 7 by means of a vertical feed cam 6 mounted on a lower shaft 5 and retable thereby. In this kind of device, if an upper surface 2a of feed dog 2 is set to be parallel to an upper surface 8 of the needle plate at a phase where the upper surface 2a of the feed dog 2 appears above the upper surface 8 of the needle plate, the upper surface 2a is made oblique with respect to the surface 8 of the needle plate during a fabric feed operation, because a pin 4 is positioned under the upper surface 2a of the feed dog 2.
As a result of the pin's position the fabric feeding efficiency is reduced and sewing mistakes such as seam shrinkage are created. is obtained by keeping the upper surface of the feed dog parallel to the upper surface of the needle plate so as to draw a square locus.
There have been proposed various attempts for providing the above mentioned square locus in the feed mechanism of the sewing machine of the swingable lever type. However, those attempts have been complicated or involved with structual difficulties.